subroutine addpt(j,nadj,madj,x,y,ntot,eps,ntri,incAdj)
# Add point j to the triangulation.
# Called by master, dirseg.

implicit double precision(a-h,o-z)
dimension nadj(-3:ntot,0:madj), x(-3:ntot), y(-3:ntot)
logical didswp

# Put the new point in, joined to the vertices of its
# enclosing triangle.
call initad(j,nadj,madj,x,y,ntot,eps,ntri,incAdj)

# Look at each `gap', i.e. pair of adjacent segments
# emanating from the new point; they form two sides of a
# quadrilateral; see whether the extant diagonal of this
# quadrilateral should be swapped with its alternative
# (according to the LOP: local optimality principle).
now = nadj(j,1)
nxt = nadj(j,2)
ngap = 0

repeat {
    call swap(j,now,nxt,didswp,nadj,madj,x,y,ntot,eps,incAdj)
    n = nadj(j,0)
    if(!didswp) {     # If no swap of diagonals
        now  = nxt    # move to the next gap.
        ngap = ngap+1
    }
    call succ(nxt,j,now,nadj,madj,ntot)
}
until(ngap==n)

return
end